Radio frequency identification (RFID) is gaining in popularity in applications such as security, inventory management, access control, etc. As a sub-category, near field communication (NFC) using the same carrier frequency as RFID in the High-Frequency (HF) range (13.56 MHz) are used in applications such as wireless sensors. The number of NFC-enabled smart phones is growing as well as the various applications of passive or active transponders (RFID tags/NFC tags). Current RFID/NFC loop antennas used in RFID/NFC tags resonate in the 13.56 MHz range and are typically dipole antennas with a rectangular or circular shape. The spatial response of the dipole antenna is two-directional with maximums when the reader's antenna and the tag antenna are parallel and nulls when they are perpendicular.
If a 3-dimensional (3D) response is required, e.g. when the object carrying the RFID/NFC tag is placed in an arbitrary position or moving in an arbitrary direction, two antennas that are substantially orthogonal to each other are required. Such a combination is difficult to fabricate, tune, and match to the RFID/NFC chip and will most likely require a custom Application Specific Integrated Circuit (ASIC). Because a typical battery is cylindrical, the combination is further complicated if the antenna is required to be placed on a cylinder.
Accordingly, a need exists for a single omni-directional antenna for a cylindrical body for RFID and/or NFC applications.